<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        .box {
            width: 1200px;
            height: 480px;
            background-color: pink;
            margin: 0px auto;
        }

        .purple {
            float: left;
            width: 280px;
            height: 480px;
            background-color: purple;
        }

        .blue {
            float: left;
            width: 920px;
            height: 480px;
            background-color: skyblue;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="purple"></div>
        <div class="blue"></div>
    </div>
</body>
</html>